The rotary transfer assemblies known from the state of the art are either axial transfer assemblies in which the fluid is passed along the axis of rotation or parallel thereto into the rotating machine part, or radial rotary transfer assemblies. Japanese patent specification JP 09196265 A which the present application takes as its basic starting point discloses such a radial rotary transfer assembly in which the fluid is passed from the stationary machine part into the rotating part in a direction perpendicular to the axis of rotation of the rotating part. In that respect, provided on the rotating part, also referred to hereinafter as the rotor, are two annular projections having axial sealing surfaces whose surface normals point in the direction of the axis of rotation and which extend in an annular configuration around the axis of rotation of the rotor. In that arrangement the sealing surfaces of the two annular projections face towards each other. The sealing surfaces of two sliding rings bear against the sealing surfaces of the rotor. The sliding rings are secured to the stationary part to prevent them from rotating with the rotor and their sealing surfaces are pressed against the sealing surfaces of the rotor by means of springs which are supported against a portion of the stationary part. The fluid is fed through a duct between the two sliding rings in a direction perpendicular to the axis of rotation of the rotor. The fluid is thus prevented from escaping by means of the sealing surfaces, which bear flat against each other, of the rotor and the two sealing rings, and by seals between the stationary part and the sliding rings.
The rotary transfer assembly known from JP 09196165 A is of a very complex and bulky structure. The part which carries the sliding sealing surfaces and which is connected to the shaft comprises two axially spaced rotor rings, with each of which is associated a respective sliding ring. The rotor rings have to be fixed on the shaft in sealed relationship. Associated with each rotor ring is its own sliding ring which admittedly does not rotate therewith but which is arranged on the shaft in an axially floating and resiliently biased condition in order always to ensure sealing contact in respect of its sliding sealing surfaces, irrespective of any component and assembly tolerances. For mounting and supporting the sliding rings the stationary part has a radially inwardly projecting flange which is arranged between the sliding rings and which presses the sliding rings against the rotor ring by way of springs. That structure takes up a relatively large amount of space both in the axial and also the radial direction.
Radial (and also axial) rotary transfer assemblies are used inter alia for the internal coolant feed in machine tools. It will be noted that a disadvantage of those rotary transfer assemblies is that they are relatively bulky and correspondingly take up space on a tool spindle. That is a nuisance in particular in modern machining centers which in any case require space for tool magazines and turret heads. Retro-fitting a coolant feed by replacing a spindle without devices for the coolant feed by a spindle with corresponding devices is often not viable because of the space additionally required for the rotary transfer assembly.
In comparison with that state of the art, the object of the present invention is to structurally design a radial rotary transfer assembly in such a way that the installation thereof in machining centers and retro-fitment thereof on existing apparatuses is simplified and does not fail because of the small space available.